textproduct: Quad Cities

KEY MESSAGES

- The heat advisory continues for areas along/south of a Sigourney, IA to Aledo, IL line. Clouds and outflow boundaries from storms may suppress heat indices in some areas.

- Strong to severe storms will be possible Wednesday. The entire area is under a Marginal, level 1 out of 5, Risk for severe storms. The primary risk is damaging winds.

- There will be a near daily risk of rain through the remainder of the week as disturbances continue to move around the edge of the heat dome. However, there will be many hours of dry weather.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 133 PM CDT Tue Aug 11 2026

Through sunset isolated to low end scattered (10-25%) showers and thunderstorms will be seen. While a severe storm cannot be ruled out, it would be very localized with damaging wind being the primary risk.

Overnight, muggy conditions will be seen across the area. There may or may not be some isolated showers or storms that develop. The overall forcing is very weak if not non-existent. However, there are areas of steep lapse rates which may allow isolated nocturnal showers or even a thunderstorm to occur. For 95 percent of the area, no rain is expected.

Wednesday has the potential to be interesting.

Internally, the models are pointing to yet another storm complex developing during the night and generally moving east. The LLJ support is very weak ahead of the potential complex but does increase behind it. This may or may not be convective feedback in the various models.

The models suggest a weakly organized storm complex moving east or east southeast from the Plains as it rides the edge of the heat dome. Overall timing suggests that it would arrive in eastern Iowa shortly after sunrise and continue east southeast into Illinois and the Ohio Valley.

If this scenario is correct then two things are known; 1) the better rain chances will be during the morning and early afternoon and 2) the storm cluster should be further south than the Tuesday morning complex.

Boundaries from this complex will then provide the focus for additional diurnal development Wednesday afternoon.

Given the weaker nature of the upper level support, the overall severe risk would be conditional on Wednesday. Progged lapse rates aloft are very steep so if severe storms would develop the primary risk would be damaging winds.

The rain Wednesday morning into early afternoon would suppress temperatures and resultant heat indices for much if not all of the area. The overall situation will need to be watched and a tactical heat advisory may or may not be issued Wednesday morning.

It appears there be a brief lull Wednesday night between the diurnal convection in the afternoon and the arrival of the next system late Wednesday night. This system gives the appearance of producing a more wide-spread rain for the northern two thirds of the area.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 245 AM CDT Tue Aug 11 2026

Thursday through Monday...If the currently extrapolated short wave train along the edge of the heat dome is in the ballpark, we may have another MCS moving into the local area Thu morning with severe weather and heavy rain risks. The temperature battle will continue as well with LLVL baroclinicity and thermal ribbon wavering acrs the region for high heat or not so bad depending on the daily flux. Rainfall amounts may really add up by the weekend and early next week on the northern fringe of the heat dome from the west central plains, acrs IA/IL, and curving down acrs the eastern OH RVR Valley. Will have to watch the Thu through Friday period for heavy rain and back building MCS potential depending on LLVL boundary and convergent flow axis's lay out if long range 2 inch PWAT feed indicators are accurate.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1220 PM CDT Tue Aug 11 2026

Isolated SHRA/TSRA will fester across eastern Iowa and northern Illinois through 02z/12. Probability of a TAF site being impacted is 10 percent or less. After 06z/12 patchy fog is again expected resulting is areas of MVFR VSBYS. After 12z/12 yet another storm complex will move through parts of eastern Iowa and into Illinois bringing SHRA/TSRA with a high probability of MVFR/IFR conditions.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Heat Advisory until 8 PM CDT this evening for IAZ076>078- 087>089-098-099. IL...Heat Advisory until 8 PM CDT this evening for ILZ024>026-034- 035. MO...Heat Advisory until 8 PM CDT this evening for MOZ009-010.